Fully pumped system HW 2-way valve closes and pump stop

The EP2002 is a programmer/timer and not a thermostat (since you seemingly understand a fair bit about your system, I thought it best to say )

Anyhoo, looking at the potential root causes:
1) Problem with boiler 'stat. I can't see it being this since the boiler should be working in exactly the same way for CH and DHW - it is switched on by the 2-port valve, and that's that. If the boiler were to overheat for any reason, it would also do it for the CH.
2) Air in pipe? Unlikely, as you say. It is pumped, so air should be pushed along out of the way. Also you could expect noises like banging and thumps if it were air. And air wouldn't make your valve close.
3) Problem with DHW 2-port valve? Possibly. It would, I guess, have to be an issue with the synchro motor - for some reason it stops being powered, so the return spring closes the valve automatically and this in turn shuts power off to the pump and boiler.
4) Prob with programmer? Possibly. For some reason it stops sending a signal to the valve.
5) Cylinder 'stat? Possibly.

The best test device would be a meter, to check how far the switching power is getting - do you have a wiring centre?.

Things I'd try, tho'. On DHW setting, after the valve has turned itself off, try turning the cylinder 'stat up and down beyond the 'click' positions - see if that provokes a response. If it doesn't, then leave it high, around 65oC+

Then try manually opening the DHW 2-port valve - there should be a lever on its end. Listen to the noise as you move it and listen for a 'click' at the end of travel. Any response from pump/boiler?

That basically leaves the EP2002 - has that stopped sending an 'on' signal. You really need a test meter or possibly a test screwdriver for this.

 

Nothing specifically jumps out at me.

The boiler kettling suggests it isn't shifting its heated water fast enough, so it may be the overheat 'stat inside tripping out (does your boiler have any 'status' display?)

But, if the boiler tripped out, that shouldn't shut the valve or stop the pump (unless they are wired differently to the norm).

The sequence of control is usually: Programmer says 'ON'. This sends a live switching signal to the VALVE. The valve opens and trips a microswitch which then sends a live switching signal to both the pump and boiler.

So, if you - say - switched off the boiler by its own panel switch, the valve and pump should still run whenever the prog tells it to.

Perhaps your system is wired differently? Perhaps the prog controls the boiler first, and the boiler then controls the valves and pump? In which case a tripping overheat stat would perform these symptoms.

We need some plumbers on here!

 

Yes, if there's power going to that wee motor, it should be spinnin'.

Why didn't the CH come on, tho' - that's a bit concerning.

Blimey, little info on that valve - that must be an oldie. If so, that would suggest it doesn't have a replaceable head (Honeywell's newer 3-port valves have an obvious raised dimple on the TOP of the metal cover towards one end, and that apparently indicates it does have a replaceable head. Is yours dimpled (ooh-er, missus).

But, if the valve has failed, then that would show your symptoms. I guess it's the most likely candidate.


You CAN do this! And replace the WHOLE valve

Put some photos on here of your pipework and wiring centre, and we'll see if you get to a point where you'll feel competent to try it.

Partially draining down a system isn't the nightmare it might seem (tho' it can become one...)

 

Is there a small bump on the metal cover of the Honeywell valve? If there is, the actuator (that's the metal box containing the motor etc) can be replaced without draining down. You can also replace the just synchron motor, if that's the only problem. Your meter will tell you where the fault is.

"9243" sounds like a date code: 1992, week 43!

 

The synchronous motor has already been replaced, and judging by the wire colours, it is one of the 'cheapies' that probably has nylon gearing that does not last long. This is the easiest to change; put into manual position, undo 1 screw and twist the other bracket out of the slot, remove motor, cut wires, connect new motor and replace motor in valve. Just be sure to use a genuine Synchron motor available from our hosts about £16.

 

The head on the other valve has the 'dimple' . So if you didn't want to get a plumber out yet, or didn't want to drain down the system, then it is an easy DIY job to replace the motorhead.

Having done just this a week ago on a 3-porter, a few tips should you chose to go ahead...

Cut the power!

The whole top metal box which contains the motor and switches and everything is secured by only 2 screws to the actual brass valve part - have a surf on t'net to see where these screws are. (There's a screw holding the motor close to one of these screws, so don;t get confused...)

Once these two screws are removed, the whole 'head pulls off - give it a good tug and wobble.

Leave the wiring connected until you've done this (in case you panic and decide to stop...)

Once the head is off, open the lid of the wiring centre - take some photos, and also write down the colours to each terminal - 4 colours and the earth.

Ok, BIG TIP (from Lucia Fermi ) - when you are ready to swap the wires over, CUT the 4 wires inside the centre a couple of inches from the terminal. That will leave a couple of inches of each colour still connected so you can't possibly go wrong! One at a time undo a terminal, pull out the old wire end and fit the new. Repeat...

To fit the new head, look inside the motor spindle slot to see how it's aligned - judge how that matches the spindle coming out of the valve body. A tip I saw on t'net is to pull the manual lever all the way against the spring, position the head on the spindle, and jiggle it on - it may need a firm push, and oscillate it slightly each way as you press it on. Release the manual lever as you do this and the spindle slot will rotate and you'll hopefully get it to match the valve spindle. If it doesn't seem to press on, pull the lever again and release.

It WILL go on!

 

Personally, before doing any of these things i would check that wire coming frome the Synchron motor to the brown (live) of the valve, as it looks like when previously changed, was not secured properly. Might save you a lot if time. Would explain poss why valve opens for short time then closes again, generally when the motor has gone it doesn't work at all.

Secondly, the easiest way to deal with the wiring is to cut the cable (after dead testing it) outside of the wiring centre about half way along the cable, use a purpose designed cable joiner, then all you have to do is match up the colours. Make sure you switch off the system at spur and not clock, as Gray or orange will be permanent live.

Lastly, if you can help it, I would avoid draining the system, sounds like an old boiler and if it kettles there is probably some sludge floating about. If you drain you may block the cold feed and not be able to refill. That will be a nightmare.
Hope some if this is useful.

Good luck

 

Hi, This might help with the boiler kettling, it certainly quietened my heating system:

http://www.screwfix.com/p/fernox-f2-central-heating-boiler-noise-silencer-500ml/44452